Manufacture of treads



April 1943- w. H. SAYRE MANUFAQTURE OF TREADS Filed March :51, 1941 all i!!! INVENTOR MLL/AM H. JAY/PE ATTORNEY5 Patented Apr. 27, 1943 MANUFACTURE OF TREADS William n. Sayre, Essex Fells, N. 1., assignor to American Abrasive Metals Company, Irvington, N. .L, a corporation oLNew York -Application March 31, 1941, Serial No. 386,081 8 Claims. (Cl. 34-5) This invention relates to improvements in the manufacture of non-slip, wear-resistant treads adapted for pedestrian and other traflic, such as treads on steps and Stairways, tread surfaces for floors, ramps, walks. runways, running boards,- platforms, etc., comprising abrasive particles bonded-1 byresinous material.

This application is in part a continuation of my prior application Serial No. 202,581, filed April-18,1938. I v

The treads consist ofv abrasive particles bonded together'by suitable hard, synthetic resinous or plastic materials and one or more fibrous materials, together-with pigments, fillers, -etc., if desired. the treadsfwhen properly made, as hereinafter expiain ii-ombining high resistance to wear,'high resistance to moisture, non-slip characteristics until}, quite? completely worn away, capability ot-.'beingproduced in various attractive colors and designs,,- resistance to shattering or cracking-high'iihpact'and fiexural strength, high water-resistance and absence of cold or plastic fiow.

The treads may vary somewhat in their composition but in general they will contain abrasive or abrasion-resisting particles together with fibrous materials suitably bonded to give a hard, dense, moisture-resistant and long-wearing tread. The abrasive particles are advantageously bonded together with a synthetic'resin binder which is heat hardenable and which in a heathardened state gives, with the other constituents of the tread, a tread capable of withstanding shocks and vibration and also substantially free from cold flow under normal service conditions.

Dififerent abrasion resisting materials can be employed in making the treads as will be readily understood and the size and proportion of abrasive grains can also be somewhat varied as can also the nature and proportions of fibrous materials, etc.

In order to obtain a suiliciently uniform mixture of the tread composition, it is advantageous to use a part at least of the resin binder in liquid form and subject the grains and fiber to prewetting therewith before compounding with other constituents such as fillers and powdered resin. When a liquid resin and a powdered resin are both used, the proportions can be somewhat varied, but the liquid resin is desirably used for prewetting the grains and fiber in amount sufll cient for that purpose.

The resins used should be such as will impart the necessary bonding action to the grains and to admixed fibers, fillers, etc. to insure a dense,

water-resistant tread after molding. The nature of the resins should also be such as will prevent undesirable flowing or cold fiow or the finished tread and also avoid undue brittleness. The liquid and powdered resins, when used, may both be thermo-reactive"or'thermo-setting resins or should be of such nature and proportions that when subjected t'o'heat hardening either during or after molding the hardened composition will have the desirable properties above mentioned.

The treads having the desirable characteristics above referred to may be produced by either hot pressing or cold pressing methods. With either method the abrasive material and the fibrous material are advantageously prewet with a liquid thermo-setting resin, e. g., a liquid A" stage phenolic resin followed by admixture of the prewetted fibrous and abrasive materials with powdered resins, e. g., a 3" stage phenolic resin along with coloring material, inert pigments and the like. In cold pressing, the mixture is pressed to the desired form and baked at a sufiiciently high temperature for a sumcient period of time to cause the reactive resin to change to the permanent inIusible and unreactive state, coalescing the entire mixture to a homogeneous, dense hard mass having high impact and flexural strength, freedom from cold flow, etc.

For hot pressing the composition is subjected to heat and pressure at the same time. At the higher temperatures the solid resin may melt or fuse with the liquid resin and facilitate the thorough intermixture and wetting of the other ingredients. With the hot pressing method the quantity of liquid resin used is advantageously considerably less than the amount used in the cold pressing method. Or, alternatively, the proportion of 'fibrous materials or inert fillers and the like may be greatly increased.

Regardless of which method is used, the final product is one in which the abrasive materials are firmly bonded together by a hard, synthetic resinous bonding material including fibrous material which has also been thoroughly wetted by the resinous material, so that the final product is not characterized by a lack of resistance to impact or of flexural strength which has been characteristic of products previously known: and, because of the proper selection of the. bonding material, is not subject to the cold or plastic flow which has been so objectionable in tread surfaces made from such materials as asphalt or mastic.

Advantageously, the treads are reinforced with metal .backings such as channeled metal backings, wire mesh or other form of reinforcement,

although for special purposes, such as floor tiles or the like, particularly where they are to be permanently set in concrete orother foundation maried over a wide range, for example, from as little" as to as much as 80% or more. Wear reslstance is, roughly, proportional to the abrasive content, and to the quality of the abrasive used, such abrasives as aluminum oxide giving greater wear than the inxepensive abrasives such as flint or sand. a

The typeand quantity oi synthetic resin, the efiective bonding agent, also maybe widely varied. Somewhere around 12 to of resin is advantageously used, although the amount of resin may be much less than this, for example, 8% or even-less, or much greater than this, for example, as much as 50% or more.

The proportions of liquid resin and solid resin used can also be varied depending upon the proportions of other ingredients. A proportion ot 2 parts of liquid resin to 14 parts oi dry, powdered resin has given excellent results,-but these proportions can be somewhat varied. With too high a proportion of liquid; resin, the mixture may become tacky or tend to ball up or give diillculty in handling in pressing or molding. To avoid difficulties in processing and compounding the amount of liquid resin used is ordinarily as small as will effectively prewet the abrasive and fibrous materials. The proportion of liquid resin may thus vary in making difierent treads from e. g., 0.75% to e. 8.. 2.5%.

The two types of resins used, e. g., liquid and powdered resins, are thermo-setting resins or react by thermo-setting to give anappropriate bond for the tread. Thermo-setting liquid resins, that 4 is, resins which on heating are converted to a hard, iniusible condition, such as A stage phenolic resins or alkyd resins, are advantageously used, but thermo-plastic resins such as the vinyl chloride-vinyl acetate resins may be used, particularly ii. adequately plasticized with some such material as tricresyl phosphate.

of fibrous material used may also be varied over a wide range. Asbestos, for example, may be used in proportions ranging from 8% or less to as much as 50% or even more, depending upon the quality and cost of the product desired. Increasing the proportion'of asbestos increases the flexibility and strength of the treads, but tends to decrease the wearing qualities because of the accompanyingjdecrease in the proportion of abrasive material. The use of relatively large proportions oi asbestos depends upon the use of the liquid resin for prewetting the abrasive material, as unless the abrasive material is prewetted with the liquid resin, a homogeneous product containing substantial amounts of asbestos cannot "be produced. Other fibrous materials, such as wood flour, may also be used in widely varied proportions; but large quantities of wood fiour The amount of the powdered resin used may also be varied so that the total amount of resin is somewhere between 8% to 50%, advantageous- 1y 12% to 20%. The use, for example, or 14V parts of dry resin with two parts of liquid resin With the powdered resins also, thermo-settilig resins, such as a B" stage gives good results.

phenolic resin or an alkyd resin are advantageously used, but thermo-plastic resins such as the vinyl chloride-vinyl acetate resins may be used. The resins used are synthetic resins of the type which, at least when at normal temperatures, are hard and rigid and relatively free from cold or plastic flow.

Similarly, the amount and type 0! fibrous material may be widely varied. The most satisfactory fibrous material, for the production of high grade treads, which I have yet found is asbestos, although other fibrous materials, such as wood flour, linters, etc., may be used. The quantity will ordinarily only be used in the cheaper grades of products, or where treads of light weightare desired. a

-For coloring the final product, various coloring pigments, such as red iron oxide, carbon black, zinc oxide, etc., may be used in such quantities as are required to give the desired color to the final product.

Inert fillers, such as whiting, may,also be included. Where the treads are made by a cold pressing operation, the amount of such inert filler which may be used is relatively limited, because with such fi1lers, it is necessary to increase the proportion of liquid resin to an amount sufiicient to bind the inert material as well as the fibrous material and the abrasive material after pressing and prior ,to baking, and with the inclusion in the product of too much of the liquid resin, difllculties are encountered in processing because of the tendency of the product to fiow in the baking operation. Where the products are prothis reason the materials produced by hot pressing may be considerably cheaper than the products produced by cold pressing operations, although usually, because of the inclusion of filler, of lower quality.

The invention will be illustrated by the following examples, but it is not limited thereto.

Example 1.-74 parts of aluminum oxide abrasive (Aloxite), 20 to 60 mesh, are mixed with 1.5 parts of a liquid, reactive phenolic resin (Resinoid A). 8 parts of asbestos fibers inch) are then added and the mixing is continued until both the abrasive material and the asbestos are wet by the liquid resin. 2' parts of red iron oxide, and 14.5 parts of a powdered reactive phenolic resin (Resinoid B) are then added and the entire mass is subjected to further mixing until homogeneous. The temperatures and other conditions of mixing should be adjusted to'give the best results with whatever ingredients are used, more viscous resins being advantageously used at higher temperatures and less viscous resins at lower temperatures,

After the material has been thoroughly admixed the proper amount is placed in a mold, superimposed upon a suitable backing or reinforcing member, such as corrugated sheet steel or the like, and formed by pressing, for example, at 10,000 pounds per square inch, for a short time. The pressed article is then removed from the mold and baked in a frame which produces a reverse warp so that when the resin shrinks on 01 becoming concave, due to the greater shrinkus e r s n us material as compared with the rnetal'backlng. The timeand temperature "of baking willbe whatever isrequired to convert the particular resin used to the ,flnlshe'd state.

f w hile' 'with some compositions [cold molding and subseguent" baking will produce'asatisfactory "l fiwt: fills inii e a m r advantageous. t ub e se rbs i ntai hot 'moidin i w h may beonly for a short periodof time after which oldedtr' ma removed from me mold ubiected to a ki "ra to runner cease-resented? stag-or iir s't inolding, the tread ands-s a.

a ba d 's,1 ecdm 1eiebaki pe tion "arme out ramesame hot press used for ""oldingfei g;;" by m'olding the. article -in the'he'at ed press at 10,000 pounds pressurejfpr a sufll'cient time; or he hardening: may be in part carried out m the mold aria finished by subsequent baking.

. e bqi i li ain lijista f f s s te stains as the'ab sa eame; abrasive"grains can be e such asni t,'"sllica,'ietc.' 1 the tread-is made with-resin, abrasive, broiis materia' rid'icoloi without any large ade o "filleriftheprocedure"followed i's'advantageou'sly that of Example 1 with niixlng of abrasive resaa g'grhnsganw liqu id resins to; gether, of 'niinut srm wedfby'additionof I l tii i minutes pr; r rcerf which the pow; dered res"n"ir'on oxid o othefcolors'are added together he continued fior seam.- cie rit' time; "e; .{5 frniniit's -to brln'g about'isub? stanti'a'll ho ino'geneous-intermlxing.

When im ixed'co'rnpbundi sed for making the treads. contaihs fillers i'rf "addition to the ingredients mentioned above; "the mixing procedure can be some what nfodified such thatthe grairr and liquid resin are"firs't'inlxed and"the other ingredients-incl-uding' tlie fillers' separately mixed, followed by adding-the "wetted 'j'grain gradually and-- effectingfurther admixture.

ranging in size from 20 to 80 mesh, are mixed with 2 parts of a liquid thermo-setting resin. parts of asbestos fiber (about inch) are separately mixed with 41 parts whiting, 14 parts of a powdered thermo-setting resin and 8 parts of red iron oxide. The two mixtures are then admixed, with gradual addition of the coated abrasive particles to effect thorough admixture, then placed in a mold on top of a suitable backing member and pressed at a temperature of around 350 F, and 10,000 pounds pressure for a few minutes, e. g., from 4 to 15 minutes depending-upon the type of resin used. If a fast curing resin is used, the article may be completely cured during th pressing operation; while if a slow curing resin is used additional baking may be required. Upon removal from the mold, if-the tread has a metal backing, it is placed on a convex form to produce a reverse warp somewhat in excess of the warp which would be produced by the difference in shrinkage of the resin and the metal backing. As a result, when the tread cools, it retains a slight reverse warp, that is, is slightly convex. It is then run through rollers and straightened after thorough cooling, giving a tread which is flat and free from strain. This method of cooling and straightening is somewhat simpler than the method described in Example 1, because it is not necessary to provide a form for each tread during the baking operation, and it is not necessary to adjust the degree of reverse warping 7 parts suillcient' flexibilityto, or rolling or ,thetread. :mm to a flat shape. Example -tip-50 parts. of abraslvegrains; e. g., 25 Parts 01 9 1 b s r armature minum oxide abrasive, are mixed with 2 of a i u tleo tt ns;.res. f asbestos fiber, .16 parts of. solid resin'andliflpoundsh red then separately mixed mam co tedaabrasilve r de e e-breathe.... llrw se airied out in a manner similar to that desc bed in Examp 1e 2-, I if; g h l e nf' us 12 B Qi-a e vs 2 in E a p a m e amc ntaotabrasiveam e a ..m a f s d. e..s-..z =r a .tsaand saincreased am t or fibrous ma-terlalaeisqz zfi parts ofv woodflourin addition :to the, .10 Pa iah! bestos or -Example 3.

Examp .7 1 s me.... ases a; llqui. l-8 1 3 r setting resin can be used without aelm ggture of p wd us Afizena tsa-ot aluminum oxide abrasive grains (Aloxite) may be t 00 Pa s of liq id,- he mo -s tt nz' esin (Resinoid d1. 132 pa ts f. asbestos :fibBL.zflBd:-'32 p t of iron ide-1; 11E-10 PI$$3a9 abrasive rai an nb eu d w th; flfln-partseai wr slnrt at r w 1105 pa s. 0 ;1wh .t ne.-. -.1;5il par. asbestos ,fiber. audi pa ts of romoxide Kan-an increased amount of filler: can. harm d; ver: 121.0 parts iwhitine-tw tb qaparts of abrasive grain; 40 pa ts o s e fibe r-Meparts.cti-lronibxide and part r i u d .thernio'ese tinsaresim When only a liqu theme-setting resin :used: the proportions of abrasive grains,flllers,zfibrous material, etc., can be .varied andtthesm x fl and molding operationsshould; be; carried :out; under conditions ,toinsure pressing andahardeningrot the thermo-setting resin; to ,produce -the fine-t molded tread. q In the foregoing examples, the. treadimateriali has been applied vdirectlyzto 0116111613815 backing,- if a metal backing is used. Other types of backings, such as burlap, wire mesh, etc., may be used, particularly for tiles which are to be set in ce ment or the like. For stair treads or treads to be applied over surfaces which may be somewhat irregular, it is advantageous to use the metal backing to increase the structural strength and to prevent undue-"strains on the bonding material because" of surface irregularities. Where backing material such as corrugated sheet steel is used, it is advantageous to subject it to sandblasting or the like to improve the bond-be tween the resin and the metal; andgin some cases it is advantageous to use an: intermediate bonding layer of a thermo-plastic resin, rubber, or the like, either to provide sound deadening, better bonding, or for other purposes. The application of Homer H. Bashore, Serial No. 386,076, filed March 31, 1941, describes backings for treads, and methods of producing treads with backings, which may be used 'with advantage in producing the treads.

A tread typical of those described in the said Bashore application is illustratedin the appended drawing. In the tread illustrated in the drawi'ng there is provided a metal backing .l .and a tread material 2, the tread material being of the type previously discussed. Such a tread is readily produced by applying a suitable tread mixture to a corrugated or channeled sheet metal backing, and subjecting it to hot pressing, whereby the channels in the backing are flattened out more or less as shown in the attached drawing forming an interlock with the tread material.

I claim:

1'. The method of forming a non-slip, wearresistant tread which comprises wetting abrasiveresistant particles'with liquid resin, mixing the wetted abrasive-resistant particles with powdered resin and fibrous material, and curing said mixture to provide a hard tread surface of synthetic resin having abrasive-resistant particles and fibrous material embedded therein and bonded thereto.

2. The method of forming a non-slip, wearresistant tread which comprises wetting abrasiveresistant particles with liqud resin, mixing the wetted abrasive-resistant particles with fibrous material, then mixing the resultant mixture of abrasive-resistant particles and fibrous material with powdered resin. and curing the final mixture to provide a hard tread surface of synthetic resin having abrasive-resistant particles and fibrous material embedded therein and bonded thereto.

3. The method of forming a non-slip, wearresistant tread which comprises wetting abrasiveresistant particles with liquid resin, mixing fibrous material with liquid resin, mixing the wetted abrasive-resistant particles and the wetted fibrous material, mixing the resulting mixture of abrasive-resistant particles and fibrous material with powdered resin, and curing the final mixture to provide a hard tread surface of synthetic resin having abrasive-resistant particles and fibrous material embedded therein and bonded thereto.

4. The method of forming a non-slip, wearresistant tread which comprises wetting abrasiveresistant particles with liquid thermo-settlng resin, mixing the wetted abrasive-resistant particles with powdered thermo-setting resin and fibrous material, and curing said mixture under heat and pressure to provide a hard tread surface of synthetic resin having abrasive-resistant particles and fibrous material embedded therein and bonded thereto.

5. The method of forming a non-slip, wearresistant tread which comprises wetting abrasiveresis'tant particles with liquid thermo-setting resin, mixing fibrous material with liquid thermosetting resin, mixing the wetted abrasive-resistant particles and the wetted fibrous material, mixing the resulting mixture of abrasive-resistant particles and fibrous material with powdered thermo-setting resin, and curing the final mixture under heat and pressure to provide a hard tread surface of synthetic resin having abrasiveresistant particles with liquid resin, mixing the therein and bonded thereto.

6. The method of forming a non slip, wearresistant tread which comprises wetting abrasiveresistant particles with liquid resin, mixing the wetted abrasive-resistant particles with powdered resin and asbestos fiber, and curing said mixture to provide a hard tread surface of synthetic resin having abrasive-resistant particles and asbestos fiber embedded therein and bonded thereto.

7. The method of forming anon-slip, wearresistant tread which comprises wetting'abrasive resistant particles with liquid, resin, mixing the wetted abrasive-resistant 'particlii isxwithasbestos fiber, then mixing the resultant mixture of abrasive-resistant particles and asbestos fiber with powdered resin, and curing the final mixture to provide a hard-tread surface of synthetic resin having abrasive-resistant particles and asbestos fiber embedded therein and bonded thereto.

8. The method of forming a non-slip, wearresistant tread which comprises wetting abrasiveresistant particles with-liquid heat-reactive resin, mixing the wetted abrasive-resistant particles with powdered heat-reactive resin and fibrous material, and curing said mixture to provide a hard tread surface of synthetic resin having abrasive-resistant particles and fibrous material embedded therein and bonded thereto.

WILLIAM H. SAYRE.

- CERTIFICATE OF CORREGTiON. Patent No. 2,317,960. April 27,- 9 +5- WILLIAM H. SAYRE.

It is hereby certified that error appears in the printed specificetion U of the above numbered patent requiring correction at follows lage h sec? ond column, line 15, claim 5, for "resistant particles-with liquid resin,

mixing the" read --resistant particles and fibrous na'te ria1 embeddedand that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of June, A. D. 1915.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents. 

